Swash plate type refrigerant compressor of a typical structure is disclosed by, e.g., Publication of Unexamined Japanese Patent Application No. 60-209,674 (1985). The compressor of this type includes front and rear cylinder blocks axially combined and having formed therein a plurality of cylinder bores and a center swash plate compartment, a reciprocable double-headed piston received in each of the cylinder bores, a drive shaft rotatably supported in the cylinder block assembly, and a swash plate fixedly mounted on the drive shaft at an inclined angle for rotary wobbling movement in the swash plate compartment. Each piston is held by the swash plate by way of a pair of front and rear hemispherical shoes interposed between the front and rear slant surfaces of the swash plate and shoe receiving recesses formed in the piston at its intermediate portion, respectively, so that the wobbling movement of the swash plate is converted into reciprocating movement of the piston in its associated cylinder bore for compression of refrigerant gas introduced into the cylinder bore.
In operation of the compressor, flat or non-spherical face of the shoe is kept in sliding contact with the slant surface of the rotating swash plate. Since the plate rotates at a higher peripheral speed at a location thereof farther from the axis of the drive shaft, the flat face of the shoe will be subjected to the influence of such different peripheral speeds of the swash plate, which results in a turning moment causing the shoe to be rotated or spun on the slant surface of the plate. If the piston is made of soft material such as aluminum, the shoe receiving recess of the piston tends to wear rapidly by sliding contact with the shoe which is periodically pressed against the recess while spinning. An increase of the wear to such an extent that an excessive clearance is formed between the shoe and the piston will allow noise to be developed by the shoe striking the swash plate and the piston during operation of the compressor. Thus, the conventional swash plate type compressor has had a problem in durability.